Ejector

Abstract

An ejector includes a nozzle having a fluid passage circular in cross section. The fluid passage includes a throat portion smallest in cross-sectional area, a divergent portion that becomes larger in cross-sectional area toward a downstream side from the throat portion, and an ejection port that is provided at a downstream end of the divergent portion. A passage wall surface of the divergent portion includes a recess portion that is recessed from within outward in a radial direction of the passage wall surface. The recess portion is located adjacent to the ejection port, and the recess portion extends continuously in a circumferential direction of the passage wall surface to enclose the fluid passage and have an annular shape. Accordingly, noise due to an expansion wave of the ejected fluid can be reduced.

The invention claimed is: 
     
       1. An ejector comprising:
 a nozzle that ejects a fluid, wherein 
 the nozzle includes therein a fluid passage having a circular shape in cross section, 
 the fluid passage includes:
 a throat portion that is smallest in cross-sectional area of the fluid passage, wherein the fluid is depressurized downstream thereof; 
 a divergent portion that becomes larger in cross-sectional area toward a downstream end from the throat portion in a flow direction of the fluid; and 
 an ejection port that is provided at the downstream end of the divergent portion and is a port through which the fluid in the divergent portion is ejected, 
 
 a passage wall surface of the divergent portion includes a recess portion that is recessed from within outward in a radial direction of the passage wall surface, a first uninterrupted surface extending between the throat portion and the recess portion, and a second uninterrupted surface extending from the recess portion to the election port, 
 the recess portion is located adjacent to the ejection port, 
 the recess portion extends continuously in a circumferential direction of the passage wall surface to have an annular shape, 
 a shape of the recess portion in cross section perpendicular to the circumferential direction is a V shape, and 
 the V shape has a larger dimension in width along the flow direction than depth. 
 
     
     
       2. The ejector according to  claim 1 , wherein the recess portion is provided at a position from 5 to 10% of a length of the divergent portion in its flow direction away from the ejection port toward the throat portion of the fluid. 
     
     
       3. The ejector according to  claim 1 , wherein the recess portion has a sectional shape perpendicular to the circumferential direction such that an angle of a recess corner part positioned at a bottom part of the recess portion is smaller than an angle of a protrusion corner part positioned at a boundary between the passage wall surface and the recess portion. 
     
     
       4. The ejector according to  claim 1 , wherein the first uninterrupted surface of the divergent portion includes a conical surface and the recess portion is recessed from the conical surface in the radial direction. 
     
     
       5. An ejector comprising:
 a nozzle that ejects a fluid, wherein 
 the nozzle includes therein a fluid passage having a circular shape in cross section, 
 the fluid passage includes:
 a throat portion that is smallest in cross-sectional area of the fluid passage, wherein the fluid is depressurized downstream thereof; 
 a divergent portion that becomes larger in cross-sectional area toward a downstream end from the throat portion in a flow direction of the fluid; and 
 an ejection port that is provided at the downstream end of the divergent portion and is a port through which the fluid in the divergent portion is ejected, 
 
 a passage wall surface of the divergent portion includes a recess portion that is recessed from within outward in a radial direction of the passage wall surface, a first uninterrupted surface extending between the throat portion and the recess portion, and a second uninterrupted surface extending from the recess portion to the ejection port, 
 the recess portion is located adjacent to the ejection port, 
 the recess portion extends continuously in a circumferential direction of the passage wall surface to have an annular shape, and 
 a shape of the recess portion in cross section perpendicular to the circumferential direction is a V shape. 
 
     
     
       6. The ejector according to  claim 5 , wherein the recess portion is provided at a position from 5 to 10% of a length of the divergent portion in its flow direction away from the ejection port toward the throat portion of the fluid. 
     
     
       7. The ejector according to  claim 5 , wherein the recess portion has a sectional shape perpendicular to the circumferential direction such that an angle of a recess corner part positioned at a bottom part of the recess portion is smaller than an angle of a protrusion corner part positioned at a boundary between the passage wall surface and the recess portion. 
     
     
       8. The ejector according to  claim 5 , wherein the first uninterrupted surface of the divergent portion includes a conical surface and the recess portion is recessed from the conical surface in the radial direction.